Statement of the Technical Field
The present invention relates generally to Radio Frequency Identification (RFID) systems. More particularly, the present invention relates to antennas for RFID systems which facilitate transmission and reception of radio frequency signals having various polarizations.
Description of the Related Art
RFID systems use wireless technology to automatically extract identification information from tags that are typically attached to objects or people. The information is electronically stored in the tag and is usually transmitted by the tag in response to an external electromagnetic stimulus. The tags are available in a variety of formats but are most commonly powered using electromagnetic induction methods. In such systems, the energy for powering the tag and for wirelessly transmitting the stored information is derived from an external applied electro-magnetic field which is produced by a reader antenna i.e., an antenna which is connected to a RFID reader system). Accordingly, each RFID tag will include an antenna to harvest energy from the externally applied electromagnetic field and to broadcast the information stored on the tag.
One of the main challenges in a practical RFID system is the ability to generate an applied external electromagnetic field that has good coverage throughout a desired area (e.g., a room or a hallway). One suggested solution to this problem is a steerable phased array antenna system which can be used advantageously to track the position and trajectory of an RFID tag within a detection zone. For example, such a steerable phased array antenna RFID tag locater and tracking system is disclosed in US Patent Publication No. 20130099898 A1.